Track and Football Field Drilling and Grouting Project

As a follow-on assignment to our work at Hanna Elementary, Brierley Associates’ AML team was retained to mitigate subsidence features originating from abandoned underground mine workings beneath the football field and track. The depth to the voids vary from 132 to 226 feet below ground surface. Subsidences would routinely appear in the football field as well as the surrounding areas of the school. The project also involved removal of the existing athletic field facilities, and construction of new replacement facilities. Close work coordination with the investigation team and the contractor responsible for removal of the existing athletic facilities and reconstruction was key to project success and required both teams to work side by side.

Since the exact location of mine workings that could be backfilled with Brierley’s high mobility grout mixture was unknown, our initial plan was to layout the exploration boring plan consisting of 168 locations spread out over 4 acres using a grid approach that took into account the estimated dimensions of the room and pillar mining. During the investigation, grouting and confirmation program, over 300 borings, both vertical and angled were completed. Information obtained indicated historic mine roofs ranged from about 60 feet to 220 feet below ground surface.